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How many species of the confusing shrub toropapa are disguised in the bush?

Toropapa (Alseuosmia) is a genus of shrubs found only in New Zealand. Toropapa has been confusing botanists for over 100 years because they show extreme variation in leaf shape – even between plants considered to be the same species from a single location! Te Papa scientists Lara Shepherd and Leon Perrie, along with the Department of Conservation’s Andrew Townsend, recently returned from a fieldtrip collecting samples of toropapa.

The extreme variation in toropapa has made it very difficult for botanists to determine the exact number of species. Our fieldtrip was focused on Northland, which is the hotspot for toropapa leaf variation. Currently there are only three toropapa species recognised from Northland.

The photos below show the range of leaves we saw. How many species do you think there are?

Toropapa, Wellsford. Photo by Leon Perrie. Te Papa

Toropapa, Wellsford. Photo by Leon Perrie. Te Papa

Toropapa, Bream Head. Photo by Leon Perrie. Te Papa

Toropapa, Wellsford. Photo by Leon Perrie. Te Papa

Toropapa, Wellsford. Photo by Leon Perrie. Te Papa

Toropapa, Whangarei. Photo by Leon Perrie. Te Papa

Toropapa, Bream Head. Photo by Leon Perrie. Te Papa

Toropapa, Wellsford. Photo by Leon Perrie. Te Papa

Toropapa, Puketi. Photo by Leon Perrie. Te Papa

Toropapa, Whangarei. Photo by Leon Perrie. Te Papa

Toropapa, Kerikeri. Photo by Leon Perrie. Te Papa

Toropapa, Peria. Photo by Leon Perrie. Te Papa

Toropapa, Opua. Photo by Leon Perrie. Te Papa

Toropapa, Whangaroa. Photo by Leon Perrie. Te Papa

Toropapa, Whangaroa. Photo by Leon Perrie. Te Papa

Toropapa, Omahuta. Photo by Leon Perrie. Te Papa

Toropapa, Mangangina. Photo by Leon Perrie. Te Papa

To add to the confusion, the leaves of some toropapa plants show a remarkable resemblance to completely unrelated species, such as maire, porokaiwhiri (pigeonwood), ramarama, and horopito. A photo of one toropapa plant that I loaded on the citizen science platform NatureWatch even tricked several experts into thinking it was ramarama!

It has been suggested that this is a case of mimicry whereby palatable plants, in this case toropapa, mimic unpalatable plants to avoid being eaten by browsing animals.

We will now use the samples that we collected to study the genetics and morphology of toropapa. This will help us determine how many species there are and hopefully allow us to understand how mimicry has evolved in the genus.

This information will then be used to assess the threats facing each species and whether any of them require conservation management.

Thanks Bruce. Yes, that species is Alseuosmia pusilla and I have been fooled many times into thinking it is Pseudowintera colorata. The trick is to turn the leaves over – P. colorata is white underneath while A. pusilla is not.

Fascinating. Ive noticed similar variation and mimicry amongst the toropapa where I live at East Cape and its only the flowers or fruits that give it away as an Alseuosmia . Runaway deer numbers are eliminating this and other sub canopy species before they can be studied .

Wow this is so interesting! The ALS mac and ALS que that we saw with the Te Papa team in Waima were the forms I often see on my travels through the Northland bush. I could never have imagined the variety that I’ve seen in photos (above). Great work team Te Papa, it was very cool to be part of this, and I look forward to the results of the genetics work.

Thanks for your help Reuben! We found most morphological diversity in eastern and northern Northland rather than your part of the country. However, the long skinny form seemed to be centred in western Northland, around Warawara and Omahuta.

Since this is a public venue I would like to suggest an amendment regarding the phrase “… in this case toropapa, mimic unpalatable plants to avoid being eaten by browsing animals.” That makes it read as if toropapa consciously do something to avoid a future outcome. This might work with ‘Intelligent Design’ theory but there is no empirical evidence, as yet, that evolution works through teleological (purposeful) mechanisms. Best to avoid teleological language unless one is really making such an assertion.

Thanks for your comment John. I’m certainly not suggesting toropapa is making a decision to mimic something else. To me it seems more likely that some of the morphological variation in toropapa, by chance, resembles other species and this provided a selective advantage over other toropapa forms.

Very nice pictures. Fascinating variety of vegetative growth and hope you can sort them out. The genus is certainly significant for its endemism. As Heads (2017) pointed out, it is an example of a New Zealand genus that does not nest within an Australian group as may be expected if it were the result of chance dispersal from Australia. One systematic study suggests that Alseuosmia is the sister group of Wittsteinia (one species in Victoria and one in New Guinea). Another classic case of Mesozoic vicariance.